U.S. patent number 10,751,875 [Application Number 15/993,624] was granted by the patent office on 2020-08-25 for rotatable mobile robot for mapping an area and a method for mapping the same.
This patent grant is currently assigned to INDOOR ROBOTICS LTD. The grantee listed for this patent is Indoor Robotics Ltd.. Invention is credited to Doron Ben-David, Amit Moran.
United States Patent |
10,751,875 |
Ben-David , et al. |
August 25, 2020 |
Rotatable mobile robot for mapping an area and a method for mapping
the same
Abstract
The subject matter discloses a mobile robot configured to map an
area, comprising a body, two or more distance sensors, configured
to collect distance measurements between the mobile robot and
objects in the area, a rotating mechanism mechanically coupled to
the body and to the two or more distance sensors, said rotating
mechanism is configured to enable rotational movement of the two or
more distance sensors and a processing module electrically coupled
to the two or more distance sensors and to the rotating mechanism.
The processing module is configured to process the distance
measurements collected by the two or more distance sensors and to
instruct the rotating mechanism to adjust a velocity of the
rotational movement, said velocity is adjusted according to the
distance measurements collected by the two or more distance
sensors.
Inventors: |
Ben-David; Doron (Ramat-Gan,
IL), Moran; Amit (Tel-Aviv, IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
Indoor Robotics Ltd. |
Ramat-Gan |
N/A |
IL |
|
|
Assignee: |
INDOOR ROBOTICS LTD (Ramat-Gan,
IL)
|
Family
ID: |
68694996 |
Appl.
No.: |
15/993,624 |
Filed: |
May 31, 2018 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190366542 A1 |
Dec 5, 2019 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G05D
1/0238 (20130101); B25J 9/1664 (20130101); G05D
1/0219 (20130101); B25J 9/1697 (20130101); G05D
2201/0207 (20130101); Y10S 901/09 (20130101); Y10S
901/47 (20130101); Y10S 901/01 (20130101) |
Current International
Class: |
G05B
15/00 (20060101); G05B 19/00 (20060101); B25J
9/16 (20060101); G05D 1/02 (20200101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Oh; Harry Y
Attorney, Agent or Firm: Soroker Agmon Nordman
Claims
The invention claimed is:
1. A mobile robot configured to map an area, comprising: a body;
two or more distance sensors, configured to collect distance
measurements between the mobile robot and objects in the area; an
actuator mechanically coupled to the body and to the two or more
distance sensors, said actuator is configured to enable rotational
movement of the two or more distance sensors; a controller
electrically coupled to the two or more distance sensors and to the
actuator, said controller is configured to process the distance
measurements collected by the two or more distance sensors and to
instruct the actuator to adjust a velocity of the rotational
movement according to the distance measurements collected by the
two or more distance sensors.
2. The mobile robot according to claim 1, wherein the two or more
distance sensors are four distance sensors arranged such that each
sensor points at substantially 90 degrees from the other
sensors.
3. The mobile robot according to claim 1, wherein the two or more
distance sensors are configured to emit light towards objects in
the area and measure a duration of time that the light travels to
the object and back.
4. The mobile robot according to claim 1, further comprises an
inertial measurement unit (IMU) configured to measure the body's
specific force and angular rate.
5. The mobile robot according to claim 1, further comprises a
camera configured to capture images of the area, wherein the
controller is electrically coupled to the camera, said controller
receives the captured images from the camera to estimate distance
covered by the mobile robot while mapping the area, to assign a
location to the distance measurements collected by the two or more
distance sensors.
6. The mobile robot according to claim 1, further comprises a
memory configured to store one or more rules concerning adjusting
the velocity of the rotational movement, wherein the controller is
electrically coupled to the memory for adjusting the velocity
according to the one or more rules.
7. The mobile robot according to claim 6, wherein the one or more
rules comprise reducing the velocity when the collected
measurements show distance higher than a predefined threshold.
8. The mobile robot according to claim 1, further comprises a
sensor housing configured to house the two or more distance
sensors, wherein the sensor housing is secured to the body in a
manner than enables rotating the sensor housing and the two or more
distance sensors.
9. The mobile robot according to claim 1, wherein the two or more
distance sensors are evenly distributed.
10. The mobile robot according to claim 9, wherein the rotational
movement is limited to a predefined angle defined by the number of
the two or more distance sensors.
11. The mobile robot according to claim 1, wherein the actuator is
configured to move the two or more distance sensors in a rotational
movement relative to the body of the mobile robot.
12. The mobile robot according to claim 1, wherein the actuator is
configured to move the two or more distance sensors in a rotational
movement applied synchronously to the body of the mobile robot.
13. The mobile robot according to claim 1, wherein adjusting the
velocity of the rotational movement comprises changing a direction
of the rotational movement.
14. The mobile robot according to claim 1, wherein the distance
measurements are collected in a first velocity prior to adjusting
the velocity of the rotational movement and collected in a second
velocity after adjusting the velocity of the rotational
movement.
15. A method for mapping an area by a mobile robot comprising
distance sensors moving with rotational movement, said method
comprising: collecting distance measurements by the distance
sensors of the mobile robot; processing the collected distance
measurements, wherein an output of said processing includes a value
used to adjust a velocity of the rotational movement of the
distance sensors; adjusting the velocity of rotational movement of
the distance sensors with said value; and collecting measurements
with the distance sensors at the adjusted velocity of the
rotational movement.
Description
FIELD OF THE INVENTION
The present invention relates to mobile robots and more
specifically to mobile robots having sensors for mapping an
area.
BACKGROUND OF THE INVENTION
One of the tasks performed by mobile robots includes mapping areas,
such as houses, rooms, fields, either indoor or outdoor. When the
area is indoor, mapping may be performed by emitting a signal to a
general direction of a wall defining the indoor mapped area, and
determining the distance from the wall in the specific direction
according to the time elapsed between emitting the signal and
detecting the signal's reflection from the wall.
One method of mapping an indoor area discloses the use of laser
beams outputted from a laser unit located on the mobile robot. The
laser beam is emitted from a laser module mounted in the mobile
robot. The laser module rotates 360 degrees around the lateral side
of the mobile robot, emitting laser at a predefined sampling
frequency, for example 4000 beams a second, with a resolution of 1
beam per degree, amounting to about 11 rounds per second.
Laser modules, such as LIDAR (Laser Imaging, Detection and Ranging)
are relatively expensive and difficult to maintain, as replacing
laser modules require technical expert, relative to replacing an
off-the-shelf camera.
SUMMARY OF THE INVENTION
It is an object of the claimed invention to disclose a mobile robot
configured to map an area, comprising a body, two or more distance
sensors, configured to collect distance measurements between the
mobile robot and objects in the area, a rotating mechanism
mechanically coupled to the body and to the two or more distance
sensors, said rotating mechanism is configured to enable rotational
movement of the two or more distance sensors, a processing module
electrically coupled to the two or more distance sensors and to the
rotating mechanism, said processing module is configured to process
the distance measurements collected by the two or more distance
sensors and to instruct the rotating mechanism to adjust a velocity
of the rotational movement, said velocity is adjusted according to
the distance measurements collected by the two or more distance
sensors.
In some cases, the two or more distance sensors are four distance
sensors arranged such that each sensor points at substantially 90
degrees from the other sensors. In some cases, the two or more
distance sensors comprise a light emitting member configured to
emit light towards the area and a photovoltaic cell configured to
measures a duration the light travelled from the light emitting
member to the object and back to a focal plane array of the
photovoltaic cell.
In some cases, the mobile robot further comprises an inertial
measurement unit (IMU) configured to measure the body's specific
force and angular rate. In some cases, the mobile robot further
comprises a camera configured to capture images of the area,
wherein the processing module is electrically coupled to the
camera, said processing module receives the captured images from
the camera to estimate distance covered by the mobile robot while
mapping the area, to assign a location to the distance measurements
collected by the two or more distance sensors.
In some cases, the mobile robot further comprises a memory module
configured to store one or more rules concerning adjusting the
velocity of the rotational movement, wherein the processing module
is electrically coupled to the memory module for adjusting the
velocity according to the one or more rules.
In some cases, the one or more rules comprise reducing the velocity
when the collected measurements show distance higher than a
predefined threshold. In some cases, the mobile robot further
comprises a sensor housing configured to house the two or more
distance sensors, wherein the sensor housing is secured to the body
in a manner than enables rotating the sensor housing and the two or
more distance sensors.
In some cases, the two or more distance sensors are evenly
distributed. In some cases, the rotational movement is limited to a
predefined angle defined by the number of the two or more distance
sensors. In some cases, the rotating mechanism is configured to
move the two or more distance sensors in a rotational movement
relative to the body of the mobile robot. In some cases, the
rotating mechanism is configured to move the two or more distance
sensors in a rotational movement applied synchronously to the body
of the mobile robot.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be more clearly understood upon reading of the
following detailed description of non-limiting exemplary
embodiments thereof, with reference to the following drawings, in
which:
FIG. 1 disclose a mobile robot mapping an area, according to
exemplary embodiments of the subject matter,
FIG. 2 shows schematic components of a mobile robot, according to
exemplary embodiments of the disclosed subject matter;
FIG. 3 shows a method of adjusting a rotational movement velocity
of components in a mobile robot, according to exemplary embodiments
of the disclosed subject matter;
FIG. 4 shows a schematic lateral view of a mobile robot, according
to exemplary embodiments of the subject matter; and,
FIG. 5 shows a schematic top view of a mobile robot, according to
exemplary embodiments of the subject matter.
The following detailed description of embodiments of the invention
refers to the accompanying drawings referred to above. Dimensions
of components and features shown in the figures are chosen for
convenience or clarity of presentation and are not necessarily
shown to scale. Wherever possible, the same reference numbers will
be used throughout the drawings and the following description to
refer to the same and like parts.
DETAILED DESCRIPTION
Illustrative embodiments of the invention are described below. In
the interest of clarity, not all features/components of an actual
implementation are necessarily described.
The subject matter in the present invention discloses a mobile
robot configured to map an area using two or more distance sensors
positioned on the mobile robot. The distance sensors emit signals,
for example light signals, and measure the distance from the object
according to the time elapsing between emission and reflection. The
two or more distance sensors rotate in an adjusted velocity,
according to commands of a processing module of the mobile robot.
The velocity of rotational movement depends on prior distance
measurements collected by the two or more distance sensors. As
opposed to mobile robots that use laser signals which rotate in a
high velocity in a single direction (clockwise or counter
clockwise), the distance sensors used by the mobile robot rotate
slower and in a controlled manner. The controlled manner enables to
adjust the resolution of distance measurements according to the
physical location of the mobile robot. For example, in case the
distance from other objects is higher than a predefined threshold,
there is a need to increase the resolution, and the processing
module of the mobile robot instructs a rotational mechanism to
decrease the rotational velocity, thus enabling to sample more
distances at generally the same direction, as elaborated below.
FIG. 1 disclose a mobile robot mapping an area, according to
exemplary embodiments of the subject matter. The area 100 is
defined by walls 102, 104, 106 and 108. The area 100 may be a room,
a field, a house, a greenhouse, either covered by a ceiling or
roof, or exposed to the sunlight. The area 100 may include objects
such as furniture, plants, animals, machines and the like. The
mobile robot 120 moves in the predefined area 100 in order to map
the predefined area 100, as the mapping includes at least a portion
of the walls 102, 104, 106 and 108 and objects (not shown).
The mobile robot 120 comprises multiple distance sensors 112, 114,
116 and 118, configured to measure the distance between the mobile
robot 120 to the walls or objects in the area 100. The multiple
distance sensors 112, 114, 116 and 118 may be a range camera, for
example a time-of-flight camera (ToF camera) configured to resolve
distance based on the known speed of light, measuring the
time-of-flight of a light signal between the camera and the subject
for each point of the image. The distance measurements collected by
the multiple distance sensors 112, 114, 116 and 118 may be stored
by a memory module of the mobile robot 120, or sent to a remote
device for further processing and/or storage via a communication
module of the mobile robot 120, as elaborated below. The multiple
distance sensors 112, 114, 116 and 118 may include two distance
sensors, or more than two distance sensors, as desired by a person
skilled in the art. The multiple distance sensors 112, 114, 116 and
118 may have identical properties, for example sampling frequency,
light wavelength and accuracy, or may be different in one aspect.
At least one of the multiple distance sensors 112, 114, 116 and 118
may be removable or replaceable as needed.
The multiple distance sensors 112, 114, 116 and 118 may point to a
predefined affixed direction, for example the direction being
parallel to an imaginary line between a center 115 of the mobile
robot 120 to the distance sensor. For example, distance sensor 112
points at direction d2 which continues imaginary line D2 between
the center 115 to the distance sensor 112. For example, distance
sensor 112 may sample point 122 located at wall 104, distance
sensor 114 may sample point 124 located at wall 106, distance
sensor 116 may sample point 126 located at wall 108 and distance
sensor 118 may sample point 128 located at wall 102. The signal
emitted by the multiple distance sensors 112, 114, 116 and 118 may
be parallel to the ground, or may be tilted, as desired by a person
skilled in the art.
The mobile robot 120 maneuvers the multiple distance sensors 112,
114, 116 and 118 in a rotational and synchronous movement in order
to map substantially the entire circumference of the mobile robot
120. an example for such rotational and synchronous movement may be
placing all the multiple distance sensors 112, 114, 116 and 118 on
a maneuverable object, for example a plate or a sensor housing and
rotating the maneuverable object in a rotational movement around in
order to enable the multiple distance sensors 112, 114, 116 and 118
to sample substantially the entire circumference of the mobile
robot. Thus, for example when the mobile robot 120 comprises three
distance sensors, each pointing outwards, about 120 degrees from
the other sensors, the rotational movement may be limited to 120
degrees at a certain point in which the mobile robot 120 is located
inside the area 100. Similarly, in case the mobile robot 120
comprises 4 distance sensors distanced equally from one another,
the rotational movement may be limited to 90 degrees. The
rotational movement of the distance sensors may be enabled using a
power source of the mobile robot, for example a battery or a
renewable energy mechanism. The velocity of the rotational movement
may be in the range of 0.01 r/s (radians per second) to 10 r/s. The
velocity may be adjusted according to properties of a mapping
mission performed by the mobile robot 120. For example, in case the
mobile robot 120 maps the area 100, the velocity of the rotational
movement may be at least 10 r/s and when the light in the area 100
as sensed by an illumination sensor located in the area 100 is
lower than a predefined threshold, the rotational movement may be
at most 1.5 r/s. Rules of adjusting the velocity of the distance
sensors' rotational movement according to mapping properties or
environmental properties may be stored in a memory module of the
mobile robot 120 or in a remote device communicating with the
mobile robot 120.
The multiple distance sensors 112, 114, 116 and 118 have a maximal
sampling frequency, for example in the range of 50-1200 Hz. Thus,
when the mobile robot 120 maps the area 100, the rotational
movement of the multiple distance sensors 112, 114, 116 and 118
results in different points in the walls captured each time. For
example, when rotating the multiple distance sensors 112, 114, 116
and 118 clockwise, the distance sensor 112 can sample point 122 and
in the next sampling, the distance sensor will sample point 123.
The physical distance between points 122 and 123 depends on the
time elapsing between two samples from the distance sensor 112, the
velocity of the distance sensor rotational movement and the
distance to the wall 104. The time elapsing between two samples
from the distance sensor 112, the velocity of the distance sensor
rotational movement dictate the angle between emissions and the
distance to the wall dictates the distance between subsequent
emissions.
The multiple distance sensors 112, 114, 116 and 118 may be Point
Time of light sensors, laser distance sensor, ultrasonic sensors,
and other point sensors. In some other cases, the distance sensors
may be depth cameras, stereo cameras, structure light cameras,
coded light cameras, ToF cameras, or a camera array. Other types of
distance sensors may be selected by a person skilled in the
art.
In some cases, the mapping process requires a specific resolution,
for example mapping the wall as the maximal distance between points
in the wall is 1.2 centimeters. As the maximal emission frequency
is limited, the mapping resolution depends on the distance to the
wall and the velocity of the rotational movement. Thus, when the
distance to the wall exceeds a predefined threshold, the mobile
robot 120 may reduce the velocity of the rotational movement.
Similarly, when the distance to the wall is lower than a predefined
threshold, the mobile robot 120 may increase the velocity of the
rotational movement. Adjusting the velocity of the rotational
movement comprises reducing or increasing the velocity. In some
cases adjusting the velocity of the rotational movement comprises
changing a direction of the rotational movement, for example from
clockwise to counter clockwise or vice versa.
A measured point must have a size in mapping. The minimal size is
defined by the scan configuration. We can assume that a point in
the map is a 0.05.times.0.05 m (5 cm2).
As a simplified example, the sensor sampling rate is 1 Hz, the
rotational velocity of 0.52 r/s (30 deg per sec). In order to
continuously scan a wall distanced 1 m from the distance sensor the
rotational velocity of the distance sensor should be 0.0499
rad/sec. The case in which all the points are distanced equally
from the distance sensor dictates that the wall is curved. In the
common case where the wall is straight, the calculation of the
rotational velocity may be performed frequently, for example once
every frame, according to the following formula:
.omega.=arctan(R/d)
where
.omega.--angular velocity (rad/sec)
R--map resolution (m)
d--measured distance by the sensor (m)
The calculation must be performed for each sensor and, probably,
the lowest velocity will be chosen in order to maintain the
constraint of continuous scan.
FIG. 2 shows schematic components of a mobile robot, according to
exemplary embodiments of the disclosed subject matter. The mobile
robot 200 comprises multiple distance sensors 240 as disclosed
above. The distance sensors 240 may be cameras. The distance
sensors 240 may comprise a signal emitting module and a sensor for
sensing the signal reflected back and measuring the time between
emitting the signal and detecting the reflected signal. The mobile
robot comprises multiple distance sensors, maneuvered using an
actuation mechanism 230 of the robot 200. The actuation mechanism
230 may be a motor, an actuator and any mechanism configured to
maneuver a physical member. The actuation mechanism 230 is coupled
to a power source, such as a battery or a renewable energy member,
such as a solar panel in case the area comprises or is adjacent to
an outdoor area accessible to the mobile robot 200.
The mobile robot 200 may also comprise an inertial measurement unit
(IMU) 210 configured to measure the robot's specific force and
angular rate. The measurements collected by the IMU 210 and by the
multiple distance sensors 240 may be transmitted to a processing
module 220 configured to process the measurements. The processing
module 220 is configured to control the rotational movement of the
multiple distance sensors 240. Thus, the processing module 220 is
electrically coupled to the actuation mechanism 230 configured to
generate the rotational movement of the multiple distance sensors
240. The processing module 220 may adjust the velocity of the
rotational movement according to at least some of the following:
(1) measurements collected by the IMU 210, (2) measurements
collected by sensors located in the mobile robot 200, (3)
measurements collected by sensors located in the area and sending
the measurements to the mobile robot 200 via communication module
270 (4) distance measurements collected by the multiple distance
sensors 240, (5) images captured by a camera module 250 located in
the mobile robot 200.
The processing module 220 may utilize a predefined set of rules
stored in a memory module 280. For example, in case the distances
measured by all the distance sensors are higher than 2 meters,
reduce velocity by 35 percent. In another example, in case the
distance measured by one of the sensors is shorter than 55
centimeters, increase the velocity to 2 m/s. In another example, in
case the temperature in the area is higher than 30 degrees Celsius,
increase the velocity of the rotational movement to the maximal
velocity possible.
In some exemplary cases, the communication module 270 sends at
least some of the collected measurements to a remote device which
outputs the adjustment of rotational movement velocity. Such remote
device may be a docking station of the mobile robot 200 or a
server, such as a web server. The output of the remote device is
converted by the processing module 220 into a command sent to the
actuation mechanism 230 to adjust the rotational movement
velocity.
FIG. 3 shows a method of adjusting a rotational movement velocity
of components in a mobile robot, according to exemplary embodiments
of the disclosed subject matter. Step 310 discloses collecting
measurements by sensors of the mobile robot. Such sensors may be
distance sensors, image capturing device, temperature sensors,
light sensors, humidity sensors, noise sensors and the like. In
case the mobile robot comprises multiple sensors of the same
functionality, for example multiple distance sensors, each sensor
of the multiple distance sensors sends the measurements along with
an identifier of the sensor. The measurements may be collected in
predefined rule, for example sampling the temperature once every 15
minutes, or collected in response to an event, for example
activating a noise sensor in response to identifying an object by
the image capturing device.
Step 320 discloses the mobile robot moving in the area. In some
cases, the measurements collected in step 310 continue to be
collected while the mobile robot moves in the area. The distance
measurements are collected by rotating the distance sensors around
an axis in the robot's body, while the robot moves in the area, for
example on a surface of the area or in the air.
Step 330 discloses processing the collected measurements. Such
processing may comprise comparing the collected measurements to a
set of rules. The output of the processing may include a value used
to adjust the velocity of rotational movement of the distance
sensors, as elaborated above. The value may be a velocity value,
for example 2 m/s, or a percentage for increasing or decreasing the
velocity of rotational movement of the distance sensors. In step
340 the processing module of the mobile robot determines sends a
command to the actuation mechanism to adjust the velocity of
rotational movement of the distance sensors. The command may be
sent via an electrical cable connecting the processing module and
the actuation mechanism, or via any other electrical, magnetic or
mechanical manner.
In step 350, the actuation mechanism adjusts the velocity of
rotational movement of the distance sensors. Such adjustment may be
implemented by adding or reducing power supplied to the actuation
mechanism. In step 360, the distance sensors collect measurements
in the adjusted velocity of rotational movement. For example, the
first velocity of rotational movement was 0.5 r/s and the adjusted
velocity of rotational movement is 0.7 r/s. Step 370 discloses
mapping the area according to measurements collected by the
distance sensors in the first velocity of rotational movement and
the adjusted velocity of rotational movement. The distance
measurements may be time-stamped, and the memory module stores the
velocity of rotational movement at each time, in order to associate
distance measurements to the velocity of rotational movement of the
distance sensor while the measurement was collected.
FIG. 4 shows a schematic lateral view of a mobile robot, according
to exemplary embodiments of the subject matter. The mobile robot
400 comprises actuation mechanism 420, 425 configured to enable
movement of the mobile robot 400 in the area. Such actuation
mechanism 420, 425 may be arms movable on a surface of the area.
The mobile robot 400 further comprises a body 410 connected to the
actuation mechanism 420, 425 using a connecting mechanism (not
shown) such as nuts and bolts, adhesives, welding and the like. The
body 410 of the mobile robot 400 comprises electrical circuitry
430, which includes a processing module, memory module and a
wireless communication module, as elaborated above.
The mobile robot 400 also comprises multiple distance sensors 440,
442, 444 located on a top section of the body 410. In some
exemplary cases, the entire body moves rotationally relative to the
ground when mapping the area using the multiple distance sensors
440, 442, 444. In some other cases, only a portion of the body, or
a sensor housing holding the multiple distance sensors 440, 442,
444, moves rotationally when mapping the area. The multiple
distance sensors 440, 442, 444 may be located at an external
circumference of the body 410, directed outwards, emitting light
towards objects in the area. The multiple distance sensors 440,
442, 444 are electrically coupled to the electrical circuitry 430,
as the electrical circuitry performs at least a portion of
processing, sending and storing the distance measurements.
FIG. 5 shows a schematic top view of a mobile robot, according to
exemplary embodiments of the subject matter. The top view shows a
body 510 of the mobile robot and a sensor housing 520 located on
top of the body 510. The sensor housing moves rotationally relative
to the ground by rotating on an axis 515, said axis 515 is
connected to both the body 510 and the sensor housing 520. The
sensor housing 520 may rotate clockwise or counter clockwise
relative to the body 510.
The sensor housing 520 is configured to hold distance sensors 530,
532, 534 and 536, configured to measure the distances between the
body 510 to objects in the area. The distance sensors 530, 532, 534
and 536 may be positioned in niches in the sensor housing, each
niche has an aperture via which the light is emitted from the
distance sensor and hits the object in the area.
It should be understood that the above description is merely
exemplary and that there are various embodiments of the present
invention that may be devised, mutatis mutandis, and that the
features described in the above-described embodiments, and those
not described herein, may be used separately or in any suitable
combination; and the invention can be devised in accordance with
embodiments not necessarily described above.
* * * * *